Currently, two expulsion systems are known, viz., the torsion system and the gear rack system. Both principles have been on the market for decades.
The gear rack system is a system comprising a drive shaft 1 arranged in a fixed position, which is provided at several positions with gear wheels 2 fixedly connected with the drive shaft. The gear wheels engage gear racks 3 associated with them. The gear racks are connected by one end to the bottom 4 of the box of the laying nest 6. The bottom is pivotably arranged and can be pushed by the gear rack from a substantially horizontal position to a substantially vertical position upon rotation of the drive shaft. As a result, the hens cannot continue sitting in the box anymore. FIGS. 1 and 2 respectively show a perspective view and a side elevational view of an example of a laying nest with gear rack expulsion system.
The torsion system comprises an expulsion plate 7 which is fixedly mounted to a tube 8. The tube is in a fixed position and is rotatable about its axis. As soon as the tube is rotated, the expulsion plate pivots along with it and pushes the hens out of the system. FIG. 3 shows a side elevational view of an example of the torsion system. In that example the expulsion plate is designed in two parts 7a, 7b which are pivotable relative to each other. Through this construction an opening via which the eggs roll from a box to the egg conveyor is not blocked by the expulsion plate 7 when the latter is situated in a position moved against a back wall of the box (see left-hand box in FIG. 3). In the right-hand box of FIG. 3 the expulsion plate is shown in an intermediate position and an end position. NL-8602398 (A) describes an example of such a torsion system.
NL-9301627 describes a system which is a kind of combination of the gear rack system and the torsion system, whereby a drive shaft arranged in a fixed position is provided with gear wheels which are engaged by movably arranged gear racks. The gear racks have one end indirectly connected to a pivotably arranged expulsion plate.